This invention relates to a silver halide photographic material having an antistatic coating.
Plastic film supports generally have a great tendency to experience static buildup, which in many cases have put various limitations on the use of these supports. To take silver halide photographic materials as an example, plastic film supports such as polyethylene terephthalate films are commonly used but they often experience static buildup, particularly at low temperatures in the winter season. Provisions against this static buildup problem bear particular importance to recent practices in the photographic industry including high-speed coating of high-sensitivity photographic emulsions and exposure of high-sensitivity photographic materials in automatic printers.
When static charge builds up on photographic materials, occasional discharging produces static marks or foreign matters such as dust particles are electrostatically deposited to produce surface defects such as pinholes which cause substantial deterioration of the quality of photographic materials. Correcting these defects results in considerable decrease in the operational efficiency. Under these circumstances, antistatic agents are customarily used in photographic materials and recently employed antistatic agents include fluorine-containing surfactants, cationic surfactants, amphoteric surfactants, surfactants or high-molecular weight compounds containing polyethylene oxide groups, and polymers having sulfonic acid or phosphoric acid groups in the molecule.
A practice that has recently gained increasing popularity in the art is to adjust triboelectric series with fluorine-containing surfactants or to provide improved conductivity by means of conductive polymers. For example, Unexamined Published Japanese Patent Application Nos. 91165/1974 and 121523/1974 disclose the application of ionic polymers having a dissociative group in the backbone chain of the polymer.
These prior art techniques, however, have the problem that their antistatic capability is markedly reduced by development and subsequent processing. This may be because the capability of antistatic agents is lost as they pass through a development step using alkalis, a fixing step under acidic conditions, and subsequent steps including washing. Hence, if processed films such as printing light-sensitive materials are subjected to a printing process, serious surface defects such as pinholes will occur on account of electrostatic deposition of dust particles. In order to deal with this problem, Unexamined Published Japanese Patent Application Nos. 84658/1980 and 174542/1986 have proposed an antistatic coating that is composed of a water-soluble conductive polymer having a carboxyl group, a hydrophobic polymer having a carboxyl group, and a polyfunctional aziridine. This approach insures that the capability of the antistatic coating is retained after photographic processing but it has been found that if a hydrophilic colloidal layer such as an antihalation layer is superposed on the antistatic coating, cracking occurs during storage to greatly impair the commercial value of the photographic material. Further, the antistatic coating has such poor adhesion to the overlying hydrophilic colloidal layer that the two layers will separate during development and subsequent photographic processing.
It has also been found that when supercontrasting agents such as tetrazolium or hydrazine compounds are used in silver halide photographic materials having this antistatic coating, the sensitivity of the photographic materials decreases with time during storage.